\begin{tikzpicture}
	\tkzDefPoints{0/0/O, 2.5/0/A, 0/2.5/B, -2.0/0/C}
	\tkzDrawSegments(O,A  O,B)
	\tkzDrawSegments[dashed](O,C)
	\tkzLabelPoints[above](B)
	\tkzLabelPoints[below](A, O, C)
\end{tikzpicture}

